Out of a whole packet of cosmos (Sensation Mixed) I planted this year at least 50 per cent turned out to be blind, i.e. no flowers. This was embarrassing as I sell plants through my WI and on our stall at the village fete. I contacted the seed manufacturer (Mr Fothergill's) but all I got was the offer of another packet (no thanks) and the excuse that there were many reasons why a plant fails to flower. But 50 per cent seems a high ratio to me. The seeds were sown March/April in plugs in a greenhouse, potted on and grew into healthy looking plants. The blind ones are very tall and healthy. Have other gardeners had this problem with cosmos.